This invention relates generally to the field of door construction. More specifically, this invention relates to doors which are constructed from metal rails and stiles.
It is well-known in door construction technology to construct doors from various combinations of door rails and door stiles made of extruded metal. Typically, a pair of spaced vertical stiles form the leading and trailing edges of the door. Two or more horizontal rails extend between the stiles to complete the principal structural elements of the door. The generally rectangular frames defined by the rails and stiles receive panels of materials such as glass to complete construction of the door.
The joining of a vertical stile and a horizontal rail must address several inherent structural and operational problems. In particular, over time, doors are subject to racking due to different portions of the door being subjected to unequal force distributions. These force distributions can arise from the door being typically supported from one stile hinged to a door frame while the remainder of the door extends outwardly to the leading or front stile in a suspended relationship. Additionally, unequal force distributions from the door operation can cause the generally planar door to twist. The vertical and horizontal orientation of the constituent stiles and rails effectively limits the amount of diagonal cross bracing that can be constructed into the door to resist racking and twisting. Furthermore, multi-pane glass panels can add significant weight to the door. The additional weight continuously places increased forces on the door thereby further increasing the tendency of the door to rack and twist.
Naturally, it is highly desirable that the assemblies for connecting the rails and stiles have sufficient mechanical integrity to limit racking and twisting of the door during operation. Furthermore, it is advantageous that rails and stiles be joined in an efficient and inexpensive configuration that does not add significant additional weight to the door.
A conventional method of affixing rails to stiles involves passing a threaded rod between the outside stiles and through the central cavity of a rail of the door. A threaded support rod is used for each rail of the door. Threaded nuts on each end of the threaded rod are tightened to draw the stiles toward each other and support the rail therebetween.
Threaded support rods have proved advantageous, but they have also exhibited certain detrimental characteristics. The support rods may loosen over time and the integrity of the joining structures is subject to expansion and contraction of the constituent components including the rails and stiles. Due to the large variety of sizes of door openings, doors of multiple widths must be constructed. Support rods of different lengths are then required for each different door width. The support rod adds additional weight to the door as the door width increases, further multiplying the stresses on the door. Generally, the edges of the stile must be open or have channels in order to facilitate access to the threaded nuts to allow tightening. For aesthetic reasons, an additional door edge piece is frequently used to cover the open edge and conceal the threaded nuts.
In another type of door construction, a clip having horizontal flanges is bolted to the door stile. The door rail is then placed over the clip and welded to the flanges. A deficiency of such a construction is that the rail cannot easily be removed from the clip or stile for repair of damaged components, and therefore the useful life of the entire door structure may be unnecessarily limited.